The present invention relates to a microencapsulated insecticidal composition for agricultural use which comprises an organophosphorus insecticide encapsulated in a wall formed of a polyurea.
Hitherto, an insecticidal composition comprising an organophosphorus insecticide microencapsulated in a wall of polyurethane wall is disclosed in Japanese Patent Kokai (Laid-Open) No. 58 - 144304 and an insecticidal composition comprising parathion microencapsulated in a wall of polyamide-polyurea is disclosed in Japanese Patent Kokai (Laid-Open) No. 48 - 4643, U.S. Ser. No. 149816.
However, no report has been made on insecticidal compositions which comprise an organophosphorus insecticide microencapsulated in a polyurea wall and which have sufficient residual effect.
Under the circumstances, the inventors have made intensive studies on insecticidal activities such as residual effect of insecticidal compositions comprising organophosphorus insecticide for agricultural use microencapsulated in polyurea wall and, as a result, found that average particle diameter, wall thickness and a ratio of an average particle diameter/wall thickness of the microcapsules have a great influence on the insecticidal activities. The present invention has been accomplished on the basis of the above finding.